This "should" work by default.
Call someone using SP2 by dialing **2 followed by a 10 digit number. Does the person receiving the call see the correct CallerID?
Make sure the OBiTalk Device is enabled as a forwarding number. Sign into GV. You must be in the Legacy GV Interface. If you're not, click on the 3 lines on the upper left and then select Legacy GV. Click on the gear ICON on the upper right then select Settings. The box to the left of the OBiTalk Device must be checked.
If that doesn't work, try deleting SP2 then re-add GV.